In recent years, it has become an important issue to recycle a product in response to growing public awareness of environmental protection and resource utilization. In a plasma display panel (hereinafter, referred to as PDP), how glass substrates, which are main components thereof, can be recycled is a major issue. There is provided a sealing member using a metal material whose reproduction is difficult in peripheral parts of the glass substrates. It is necessary to carve out the sealing member having a frame shape and central parts of the glass substrates in the process where the glass substrate is recycled.
In the PDP, a front glass substrate having a thickness of approximately 3 mm in which electrodes and the like are formed and a rear glass substrate having a thickness of approximately 3 mm in which barrier ribs, phosphors and the like are formed are placed so as to face each other so that a discharge space is formed inside, and peripheral parts thereof are sealed with a sealing member. The front glass substrate and the rear glass substrate have different sizes. At end parts of the glass substrates, the front glass substrate and the rear glass substrate are not overlapped with each other, and electrode terminals for connecting electrodes to an electronic circuit are provided. Thus, the glass substrates of the PDP include the glass-substrate sealed parts to which the sealing member is adhered, the glass-substrate central parts to which the sealing member is not adhered, and the glass-substrate end parts at which the front glass substrate and the rear glass substrate are not overlapped with each other.
As the sealing member used in the sealing, low-melting glass including a lead component by a relatively high percentage is used due to restriction for a sealing temperature. Accordingly, it is difficult to recycle the glass-substrate sealed parts to which the sealing member is adhered, while it is possible to recycle the glass substrates at the glass-substrate central parts because the sealing member is not adhered thereto. Therefore, it is necessary to segregate the glass-substrate sealed parts and the glass-substrate central parts from each other in the recycling step.
A conventional method of cutting the two glass substrates having the mentioned thickness is to scribe surfaces of the two substrates using a diamond cutter and apply a shearing force thereto along the scribe.
A method of cutting a glass substrate by scribing, which is publicly disclosed, is to etch or apply a chemical process such as chemical polishing to a part or all of a rear surface of the glass substrate, and thereafter form such a scribe that generates a crack reaching the rear surface of the glass substrate so that the glass substrate can be divided. The dividing method of this type is disclosed in the Japanese Patent Unexamined Publication No. 2004-168584.
However, the foregoing conventional method is disadvantageous in that, for example, it is time-consuming to separate the front glass substrate and the rear glass substrate from each other.
Further, in a method in which the etching is applied in advance to a surface opposite to the surface in which the scribe is formed when a glass substrate is cut, it is additionally necessary to etch the glass substrate in advance when the PDP is manufactured, which resulted in cost increase.